This invention relates generally to the art of seals, and is concerned in particular with flexible seal elements of the type employed as part of seal assemblies located between the roll end faces and the bearing chocks in a rolling mill.
In a typical rolling mill application, a roll neck is journalled for rotation in an oil film bearing. The bearing includes a sleeve keyed or otherwise fixed to the roll neck for rotation therewith. The sleeve is surrounded by and supported within a non-rotatable bushing which is in turn contained in a bearing chock. An oil film is maintained continuously between the sleeve and the bushing during operation of the mill. A seal assembly is located between the roll end face and the bearing chock. The seal assembly functions to prevent loss of oil from the bearing, and also to prevent exterior contaminants such as cooling water, mill scale, etc. from penetrating into the bearing.
In a four-high mill, experience has indicated that the exclusion of contaminants is particularly troublesome with regard to the bearings of the upper backup roll and the work rolls. This is because the downwardly facing drainage ports of their seal assemblies provide openings which can be penetrated by the contaminants being centrifugally thrown off of the rotating surfaces of underlying rolls.
An example of a typical rolling mill seal assembly is that described in U.S. Pat. No. 3,330,567 assigned to the same assignee as that of the present invention. This seal assembly includes a flexible neck seal having a circular body mounted on a tapered transition section of the roll neck, with resilient flanges extending radially outwardly from the seal body. The ends of the resilient flanges are adapted to frictionally contact surrounding shoulders on a non-rotatable seal end plate attached to the bearing chock. Oil is retained in the bearing by the sealing interface between one of the rotating resilient seal flanges and the non-rotatable seal end plate shoulder in contact therewith. Likewise, contaminants are excluded from the bearing by the sealing interface between the other of the rotating resilient seal flanges and its associated seal end plate shoulder.
The seal assembly further includes a rotatable inner seal ring carrying spacers which abut the roll end face at circumferentially spaced locations, and a non-rotatable outer seal ring which cooperates with the inner seal ring to form a sealing labyrinth between the roll end face and the seal end plate. This sealing labyrinth is drained through a drainage port at the bottom of the outer seal ring.
While this type of arrangement has operated for many years in a generally satisfactory manner, under certain conditions, for example where large amounts of liquid coolant are being applied to the work rolls, the sealing labyrinth formed by the inner and outer seal rings has been found to be inadequate, thus necessitating the addition of another flexible seal element to bridge the gap between the roll end face and the outer seal ring. In the past, such additional flexible seal elements have generally taken the form of elongated lightweight flexible extrusions which are cut to length, wrapped around the outer seal ring and held in place thereon by a metal retaining band. Such seal elements do not completely surround the outer seal rings, but rather their ends are spaced to provide a gap at the lower drainage ports to accommodate escape of contaminants from the seal assembly. While the sealing characteristics of such seal elements are by and large satisfactory, they are difficult to mount and dismantle due to the need to employ exterior retaining bands. Moreover, and this is particularly true of the upper backup roll and the work rolls, the gaps at the lower drainage ports fail to prevent contaminants from splashing up from the rotating surfaces of underlying rolls.
Accordingly, an object of the present invention is the provision of an improved flexible seal element for use on an outer seal ring which obviates or at least substantially minimizes the problems mentioned above.
A more specific object of the present invention is the provision of a flexible seal element which has a circular body portion adapted to tightly surround the outer seal ring without the need of a separate retaining band, with a circular lip sealingly contacting the roll end face, and with a drain opening in the body portion arranged to be aligned radially with the drainage port in the outer seal ring, thus allowing free drainage of the sealing labyrinth formed between the inner and outer seal rings.
A further object of the present invention is to prevent or at least substantially minimize entrance of contaminants through the drain opening in the body portion of the flexible seal element by surrounding this drain opening with a second protective lip which cooperates with an interior relatively stiff baffle element to form a labyrinth. The baffle element serves the added function of reinforcing the body portion against distortion. Thus, the drain opening, second protective lip and baffle element cooperate in providing a reinforced drain labyrinth.